1. Field of the Invention
The present invention relates to closure mechanisms for fluid vessels, and particularly to non-spill drinking vessels.
2. The Prior Art
Various closure mechanisms for fluid vessels are known in the prior art. For example, WO0197663 discloses a spill-proof closure and cup, comprising a closure assembly for fitting to an open-ended drinking vessel including a lid with a spout. The spout has a valve including a flexible portion openable to allow a flow of fluid when a pressure differential is applied to the spout by sucking thereon. In the absence of a pressure differential, the flexible portion shuts off the valve.
U.S. Patent Appln. Publication 2006/226146 discloses a drinking vessel comprising a cup and lid portion including a closure flap, which is deflectable by means of an operating handle hingedly supported on the lid to open a fluid outlet. The closure flap is resilient so that it returns to its closed position when pressure is released from the operating handle.
U.S. Patent Appln. Publication 2002/0179637 describes a safety device for a liquid-containing vessel, such as a kettle. A flap is hinged to the vessel and arranged to cover and close a fluid opening 36 when fluid presses on the flap. The flap comprises a magnet which is attracted to magnets in the region of the opening, such that the flap remains held in the closed position unless an external influence acts to open the flap. The vessel does not comprise a means for holding the flap in the open position and when pouring from the vessel, a user must continuously apply a force to the flap to hold the flap in the open position.
With the prior art devices, each time the user wishes to take a sip from the vessel, it is necessary to apply an opening force to the closure assembly, whether this force be from suction or a manually applied force, in order to allow fluid to exit the vessel. In the absence of the opening force, the closure assemblies automatically revert to the closed position.